High resolution palaeoceanography and palaeoclimatology from late Quaternary laminated sediments from the Santa Barbara Basin, California Region
The study of recent laminated sediments from the Santa Barbara Basin shows that laminae type is determined by seasonal changes in meteorology, primary production and surface circulation. The Site 893 laminites are composed of silty-clays and diatomaceous silty-clays. The annual varve may be composed...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
1998
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| Online Access: | https://eprints.soton.ac.uk/463547/ |
| Summary: | The study of recent laminated sediments from the Santa Barbara Basin shows that laminae type is determined by seasonal changes in meteorology, primary production and surface circulation. The Site 893 laminites are composed of silty-clays and diatomaceous silty-clays. The annual varve may be composed of couplets of terrigenous silt-rich and silt-poor laminae or triplets of silt-rich, silt-poor and diatom laminae. Silt-rich laminae record detrital input from winter rains. Diatom laminae mostly result from the aggregation and mass-sedimentation of upwelling generated blooms. Varves may contain multiple diatom laminae which record aspects of the seasonal cycle of primary production. These may record sedimentation under different oceanographic regimes, or multiple episodes of deposition within a single oceanographic regime. The abundance of diatom laminae during interstadials and glacials can be linked to changes in silicate availability and the composition of diatom laminae can be related to changes in upwelling strength. The ability of SEM-based analysis to discriminate between the terrigenous and biogenic laminae which form the annual varve is used to construct time-series of inter-annual and terrigenous and diatom ooze variability. Spectral analysis of laminae thickness variations indicates the presence of periodicities in both the terrigenous and diatom series of periodicities associated with the quasi-biennial oscillation (QBO) and El-Nino. Periodicities in the thickness of terrigenous laminae indicate oscillation (QBO) and El-Nino. Periodicicites in the thickness of terrigenous laminae indicate inter-annual variations in the strength of the winter Aleutian low pressure cell which exerts a strong influence on sediment delivery to the Santa Barbara Basin through modulation of rainfall. Periodicities in the thickness of diatom laminae indicate inter-annual variations in the strength of the summer North Pacific high pressure cell which drives upwelling generated primary production. Cross-spectral and phase ... |
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